Viking Therapeutics does not currently manufacture any pharmaceutical products, but is developing several products to treat metabolic and endocrine disorders. Thus, the company relies upon investments from stockholders and business partners. The company completed its Initial Public Offering in the 2nd quarter of Fiscal Year 2015, generating $22.3M in net proceeds.[5] Viking Therapeutics assumed the largest expense in 2014 from cited Research and Development costs ($21.2M), which may be related to purchase of required equipment and facilities to develop the drug candidates licensed by Ligand Pharmaceuticals in that year, including VK5211.[5]

Viking Therapeutics is yet to bring a drug to market. If one or several of their drug candidates does not pass clinical trials before one is successfully brought to market, then a significant amount of stockholders would likely sell their stocks, seriously reducing revenue and capability to continue development of VK5211. Additionally, as noted in the Form 10-Q submitted on 10 November 2016, Viking currently relies heavily upon licensed technologies by Ligand Pharmaceutics. If Viking Therapeutics were to lose this license, then its operating capability would be severely impacted.[6]

Ligand Pharmaceutics has disclosed that its royalty fee incurred upon Viking Therapeutics for production and sale of VK5211 would be 7.25-9.25% of the product revenue.[7]

Another promising drug candidate, VK2809, is expected to drive a major shift in the market cap of Viking Therapeutics and its share of the market for TRβ agonists, which is currently dominated by Madrigal Pharmaceuticals.[8] This would improve the company portfolio as a whole, and would allow for greater capitalization upon the potential success of VK5211.

Ligand Pharmaceuticals has patents filed for the manufacture and therapeutic use of certain compounds occupying several stated chemical structures, which are intended for use as selective androgen receptor modulators. The patent is filed under the following designations: US8519158 B2, US8865918, US9359285, US20070254875, US20140005186, US20150099720, and WO2005090282A1. The patents will expire on March 12, 2025. These patents effectively protect any future capitalization upon VK5211 in the market by Viking and Ligand through their licensing agreement.[9]

Oral administration of the drug to cynomolgus monkeys at daily doses varying from 0 to 75 mg/kg over 13 weeks demonstrated significant body weight gain in both males and females. After 48 days, the 75 mg/kg dose testing was halted due to toxicity concerns, but this did not negatively impact development as the dose is significantly higher than those being utilized in the Phase 2 clinical trial.[10]

In a Phase 1 clinical trial of 76 adult male humans in which the dose size was varied, a dose-dependent increase in lean body mass was observed with no significant adverse events over 21 days.[2]

The Phase 2 clinical trial, initiated on 3 November 2016, consists of 120 patients recovering from hip fracture surgery. The randomized study participants will receive either a placebo or varying dose sizes of VK5211 over a period of 12 weeks, with improved lean body mass as the primary endpoint. Other endpoints include satisfactory results in terms of quality of life, safety, and pharmacokinetics.[11]

1.
Regulation of therapeutic goods
–
The regulation of therapeutic goods, that is drugs and therapeutic devices, varies by jurisdiction. In some countries, such as the United States, they are regulated at the level by a single agency. In other jurisdictions they are regulated at the level, or at both state and national levels by various bodies, as is the case in Australia. The role of therapeutic goods regulation is designed mainly to protect the health, regulation is aimed at ensuring the safety, quality, and efficacy of the therapeutic goods which are covered under the scope of the regulation. In most jurisdictions, therapeutic goods must be registered before they are allowed to be marketed, there is usually some degree of restriction of the availability of certain therapeutic goods depending on their risk to consumers. Therapeutic goods in Australia are regulated by the Therapeutic Goods Administration, there are 5 main categories, Normal Medicines - Cough, cold and fever medicines, antiseptics, vitamins and others. Sold freely in pharmacies and some large supermarkets, red Stripe Medicines - These medicines are sold only with medical prescription. Antibiotics, Anti allergenics, Anti inflammatories, and other medicines, in Brazil, governmental control is loose on this type, it is not uncommon to buy this type of prescription medicine over the counter without a prescription. Red Stripe Psychoactive Medicines - These medicines are only with a Special Control white medical prescription with carbon copy. The original must be retained by the pharmacist after the sale, Drugs include anti-depressants, anti-convulsants, some sleep aids, anti-psychotics and other non-habit-inducing controlled medicines. Though some consider them habit inducing, anabolic steroids are also regulated under this category, black Stripe Medicines - These medicines are sold only with the Blue B Form medical prescription, which is valid for 30 days and must be retained by the pharmacist after the sale. Includes sedatives, some anorexic inducers and other habit-inducing controlled medicines, includes amphetamines and other stimulants, opioids and other strong habit-forming controlled medicines. In Canada, regulation of goods are governed by the Food and Drug Act. In addition, the Controlled Drugs and Substances Act requires additional regulatory requirements for controlled drugs, the regulation of drugs in Burma is governed by the Food and Drug Administration and Food and Drug Board of Authority. The regulation of drugs in China is governed by the China Food, Medicines for Human Use in the United Kingdom are regulated by the Medicines and Healthcare products Regulatory Agency. The availability of drugs is regulated by classification by the MHRA as part of marketing authorisation of a product, Medicines in the Republic of Ireland are regulated according to the Misuse of Drugs Regulations 1988. Controlled drugs are divided into five categories based on their potential for misuse, cD1, cannabis, lysergamide, coca leaf, etc. Use prohibited except in limited circumstances where a license has been granted, CD2, amphetamine, methadone, morphine, fentanyl, oxycodone, tapentadol, etc

2.
Investigational New Drug
–
The FDA reviews the IND application for safety to assure that research subjects will not be subjected to unreasonable risk. If the application is cleared, the drug usually enters a Phase 1 clinical trial. Regulations are primarily at 21 C. F. R, also included are any previous experience with the drug in humans. The chemical stability and activity of the product must also have been tested and this information is assessed to ensure that the company can adequately produce and supply consistent and active batches of the drug. Clinical Protocols and Investigator Information – Detailed protocols for proposed clinical studies to assess whether the initial-phase trials will expose the subjects to unnecessary risks. Finally, commitments to obtain informed consent from the subjects, to obtain review of the study by an institutional review board. A physician might submit a research IND to propose studying an unapproved drug, emergency Use IND allows the FDA to authorize use of an experimental drug in an emergency situation that does not allow time for submission of an IND. Experimental drugs under an IND must be labeled, Caution, New Drug – Limited by Federal law to investigational use, the FDA runs a medical marijuana IND program. As of 2011, four patients continue to receive cannabis from the government under the program, investigational New Drug Application Process Center for Drug Evaluation and Research, Food and Drug Administration. ICH Guidance for Industry, E6 Good Clinical Practice, Consolidated Guidance, achieving a Successful US IND Filing The Regulatory Affairs Journal. Achieving a Successful US IND Filing The Regulatory Affairs Journal, OCLC317650570,50016270,163149563 IND Forms and Instructions from the US Food and Drug Administration

3.
Pharmacokinetics
–
Pharmacokinetics, sometimes abbreviated as PK, is a branch of pharmacology dedicated to determining the fate of substances administered to a living organism. The substances of interest include any chemical xenobiotic such as, pharmaceutical drugs, pesticides, food additives, cosmetic ingredients, etc. It attempts to analyze chemical metabolism and to discover the fate of a chemical from the moment that it is administered up to the point at which it is eliminated from the body. Pharmacokinetics is the study of how an organism affects a drug, both together influence dosing, benefit, and adverse effects, as seen in PK/PD models. Pharmacokinetic properties of chemicals are affected by the route of administration and these may affect the absorption rate. Models have been developed to simplify conceptualization of the processes that take place in the interaction between an organism and a chemical substance. The various compartments that the model is divided into are commonly referred to as the ADME scheme, absorption - the process of a substance entering the blood circulation. Distribution - the dispersion or dissemination of substances throughout the fluids, metabolism – the recognition by the organism that a foreign substance is present and the irreversible transformation of parent compounds into daughter metabolites. Excretion - the removal of the substances from the body, in rare cases, some drugs irreversibly accumulate in body tissue. The two phases of metabolism and excretion can also be grouped together under the title elimination, the study of these distinct phases involves the use and manipulation of basic concepts in order to understand the process dynamics. All these concepts can be represented through mathematical formulas that have a graphical representation. The model outputs for a drug can be used in industry or in the application of pharmacokinetic concepts. Clinical pharmacokinetics provides many performance guidelines for effective and efficient use of drugs for human-health professionals, in practice, it is generally considered that steady state is reached when a time of 4 to 5 times the half-life for a drug after regular dosing is started. Noncompartmental methods estimate the exposure to a drug by estimating the area under the curve of a concentration-time graph, compartmental methods estimate the concentration-time graph using kinetic models. Noncompartmental methods are more versatile in that they do not assume any specific compartmental model. The final outcome of the transformations that a drug undergoes in an organism, a number of functional models have been developed in order to simplify the study of pharmacokinetics. These models are based on a consideration of an organism as a number of related compartments, the simplest idea is to think of an organism as only one homogenous compartment. However, these models do not always reflect the real situation within an organism

4.
PubChem
–
PubChem is a database of chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information, a component of the National Library of Medicine, PubChem can be accessed for free through a web user interface. Millions of compound structures and descriptive datasets can be downloaded via FTP. PubChem contains substance descriptions and small molecules with fewer than 1000 atoms and 1000 bonds, more than 80 database vendors contribute to the growing PubChem database. PubChem consists of three dynamically growing primary databases, as of 28 January 2016, Compounds,82.6 million entries, contains pure and characterized chemical compounds. Substances,198 million entries, contains also mixtures, extracts, complexes, bioAssay, bioactivity results from 1.1 million high-throughput screening programs with several million values. PubChem contains its own online molecule editor with SMILES/SMARTS and InChI support that allows the import and export of all common chemical file formats to search for structures and fragments. In the text search form the database fields can be searched by adding the name in square brackets to the search term. A numeric range is represented by two separated by a colon. The search terms and field names are case-insensitive, parentheses and the logical operators AND, OR, and NOT can be used. AND is assumed if no operator is used, example,0,5000,50,10 -5,5 PubChem was released in 2004. The American Chemical Society has raised concerns about the publicly supported PubChem database and they have a strong interest in the issue since the Chemical Abstracts Service generates a large percentage of the societys revenue. To advocate their position against the PubChem database, ACS has actively lobbied the US Congress, soon after PubChems creation, the American Chemical Society lobbied U. S. Congress to restrict the operation of PubChem, which they asserted competes with their Chemical Abstracts Service

5.
ChemSpider
–
ChemSpider is a database of chemicals. ChemSpider is owned by the Royal Society of Chemistry, the database contains information on more than 50 million molecules from over 500 data sources including, Each chemical is given a unique identifier, which forms part of a corresponding URL. This is an approach to develop an online chemistry database. The search can be used to widen or restrict already found results, structure searching on mobile devices can be done using free apps for iOS and for the Android. The ChemSpider database has been used in combination with text mining as the basis of document markup. The result is a system between chemistry documents and information look-up via ChemSpider into over 150 data sources. ChemSpider was acquired by the Royal Society of Chemistry in May,2009, prior to the acquisition by RSC, ChemSpider was controlled by a private corporation, ChemZoo Inc. The system was first launched in March 2007 in a release form. ChemSpider has expanded the generic support of a database to include support of the Wikipedia chemical structure collection via their WiChempedia implementation. A number of services are available online. SyntheticPages is an interactive database of synthetic chemistry procedures operated by the Royal Society of Chemistry. Users submit synthetic procedures which they have conducted themselves for publication on the site and these procedures may be original works, but they are more often based on literature reactions. Citations to the published procedure are made where appropriate. They are checked by an editor before posting. The pages do not undergo formal peer-review like a journal article. The comments are moderated by scientific editors. The intention is to collect practical experience of how to conduct useful chemical synthesis in the lab, while experimental methods published in an ordinary academic journal are listed formally and concisely, the procedures in ChemSpider SyntheticPages are given with more practical detail. Comments by submitters are included as well, other publications with comparable amounts of detail include Organic Syntheses and Inorganic Syntheses

6.
Chemical formula
–
These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH

7.
Jmol
–
Jmol is computer software for molecular modelling chemical structures in 3-dimensions. Jmol returns a 3D representation of a molecule that may be used as a teaching tool and it is written in the programming language Java, so it can run on the operating systems Windows, macOS, Linux, and Unix, if Java is installed. It is free and open-source software released under a GNU Lesser General Public License version 2.0, a standalone application and a software development kit exist that can be integrated into other Java applications, such as Bioclipse and Taverna. A popular feature is an applet that can be integrated into web pages to display molecules in a variety of ways, for example, molecules can be displayed as ball-and-stick models, space-filling models, ribbon diagrams, etc. Jmol supports a range of chemical file formats, including Protein Data Bank, Crystallographic Information File, MDL Molfile. There is also a JavaScript-only version, JSmol, that can be used on computers with no Java, the Jmol applet, among other abilities, offers an alternative to the Chime plug-in, which is no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS9. Jmol requires Java installation and operates on a variety of platforms. For example, Jmol is fully functional in Mozilla Firefox, Internet Explorer, Opera, Google Chrome, fast and Scriptable Molecular Graphics in Web Browsers without Java3D

8.
Simplified molecular-input line-entry system
–
The simplified molecular-input line-entry system is a specification in form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules, the original SMILES specification was initiated in the 1980s. It has since modified and extended. In 2007, a standard called OpenSMILES was developed in the open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. The Environmental Protection Agency funded the project to develop SMILES. It has since modified and extended by others, most notably by Daylight Chemical Information Systems. In 2007, a standard called OpenSMILES was developed by the Blue Obelisk open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, in July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is generally considered to have the advantage of being slightly more human-readable than InChI, the term SMILES refers to a line notation for encoding molecular structures and specific instances should strictly be called SMILES strings. However, the term SMILES is also used to refer to both a single SMILES string and a number of SMILES strings, the exact meaning is usually apparent from the context. The terms canonical and isomeric can lead to confusion when applied to SMILES. The terms describe different attributes of SMILES strings and are not mutually exclusive, typically, a number of equally valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol, algorithms have been developed to generate the same SMILES string for a given molecule, of the many possible strings, these algorithms choose only one of them. This SMILES is unique for each structure, although dependent on the algorithm used to generate it. These algorithms first convert the SMILES to a representation of the molecular structure. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database, there is currently no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, and these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES

9.
International Chemical Identifier
–
Initially developed by IUPAC and NIST from 2000 to 2005, the format and algorithms are non-proprietary. The continuing development of the standard has supported since 2010 by the not-for-profit InChI Trust. The current version is 1.04 and was released in September 2011, prior to 1.04, the software was freely available under the open source LGPL license, but it now uses a custom license called IUPAC-InChI Trust License. Not all layers have to be provided, for instance, the layer can be omitted if that type of information is not relevant to the particular application. InChIs can thus be seen as akin to a general and extremely formalized version of IUPAC names and they can express more information than the simpler SMILES notation and differ in that every structure has a unique InChI string, which is important in database applications. Information about the 3-dimensional coordinates of atoms is not represented in InChI, the InChI algorithm converts input structural information into a unique InChI identifier in a three-step process, normalization, canonicalization, and serialization. The InChIKey, sometimes referred to as a hashed InChI, is a fixed length condensed digital representation of the InChI that is not human-understandable. The InChIKey specification was released in September 2007 in order to facilitate web searches for chemical compounds and it should be noted that, unlike the InChI, the InChIKey is not unique, though collisions can be calculated to be very rare, they happen. In January 2009 the final 1.02 version of the InChI software was released and this provided a means to generate so called standard InChI, which does not allow for user selectable options in dealing with the stereochemistry and tautomeric layers of the InChI string. The standard InChIKey is then the hashed version of the standard InChI string, the standard InChI will simplify comparison of InChI strings and keys generated by different groups, and subsequently accessed via diverse sources such as databases and web resources. Every InChI starts with the string InChI= followed by the version number and this is followed by the letter S for standard InChIs. The remaining information is structured as a sequence of layers and sub-layers, the layers and sub-layers are separated by the delimiter / and start with a characteristic prefix letter. The six layers with important sublayers are, Main layer Chemical formula and this is the only sublayer that must occur in every InChI. The atoms in the formula are numbered in sequence, this sublayer describes which atoms are connected by bonds to which other ones. Describes how many hydrogen atoms are connected to each of the other atoms, the condensed,27 character standard InChIKey is a hashed version of the full standard InChI, designed to allow for easy web searches of chemical compounds. Most chemical structures on the Web up to 2007 have been represented as GIF files, the full InChI turned out to be too lengthy for easy searching, and therefore the InChIKey was developed. With all databases currently having below 50 million structures, such duplication appears unlikely at present, a recent study more extensively studies the collision rate finding that the experimental collision rate is in agreement with the theoretical expectations. Example, Morphine has the structure shown on the right, as the InChI cannot be reconstructed from the InChIKey, an InChIKey always needs to be linked to the original InChI to get back to the original structure

10.
PubMed Identifier
–
PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby

11.
Androgen receptor
–
The androgen receptor is most closely related to the progesterone receptor, and progestins in higher dosages can block the androgen receptor. The main function of the receptor is as a DNA-binding transcription factor that regulates gene expression, however. Androgen regulated genes are critical for the development and maintenance of the male sexual phenotype, hence, testosterone is responsible primarily for the development of male primary sexual characteristics, whereas dihydrotestosterone is responsible for secondary male characteristics. Androgens cause slow epiphysis, or maturation of the bones, steroid users of teen age may find that their growth had been stunted by androgen and/or estrogen excess. People with too little sex hormones can be short during puberty, via the Androgen receptor, androgens play a key role in the maintenance of male skeletal integrity. The regulation of this integrity by androgen receptor signaling can be attributed to both osteoblasts and osteocytes, the primary mechanism of action for androgen receptors is direct regulation of gene transcription. The androgen receptor dimer binds to a sequence of DNA known as a hormone response element. Androgen receptors interact with proteins in the nucleus, resulting in up- or down-regulation of specific gene transcription. Up-regulation or activation of transcription results in increased synthesis of messenger RNA, one of the known target genes of androgen receptor activation is the insulin-like growth factor I receptor. Thus, changes in levels of proteins in cells is one way that androgen receptors control cell behavior. One function of receptor that is independent of direct binding to its target DNA sequence, is facilitated by recruitment via other DNA-binding proteins. One example is serum response factor, a protein that activates several genes that cause muscle growth, AR acetylation is induced by androgens and determines recruitment into chromatin. The AR acetylation site is a key target of NAD-dependent and TSA-dependent histone deacetylases, more recently, androgen receptors have been shown to have a second mode of action. As has been found for other steroid hormone receptors such as estrogen receptors. Androgen receptors interact with certain signal transduction proteins in the cytoplasm, Androgen binding to cytoplasmic androgen receptors can cause rapid changes in cell function independent of changes in gene transcription, such as changes in ion transport. In humans, the receptor is encoded by the AR gene located on the X chromosome at Xq11-12. The androgen insensitivity syndrome, formerly known as testicular feminization, is caused by a mutation of the receptor gene located on the X chromosome. The androgen receptor seems to affect neuron physiology and is defective in Kennedys disease, in addition, point mutations and trinucleotide repeat polymorphisms has been linked to a number of additional disorders

12.
4-Androstenediol
–
4-Androstenediol, also known as androst-4-ene-3β, 17β-diol, is an androstenediol that is converted to testosterone. The conversion rate is about 15. 76%, almost triple that of 4-androstenedione, there is also some conversion into estrogen, since testosterone is the metabolic precursor of the estrogens. 4-Androstenediol is closer to testosterone structurally than 5-androstenediol, and has androgenic effects and it has approximately 0. 5% and 0. 6% of the affinity of estradiol at the ERα and ERβ, respectively. Patrick Arnold holds a 1999 patent on Use of 4-androstenediol to increase testosterone levels in humans

13.
5-Androstenedione
–
5-Androstenedione is a prohormone of testosterone. The World Anti-Doping Agency prohibits its use in athletes, in the United States, it is a controlled substance. 5-Androstenedione is structurally similar to 4-androstenedione, with the exception of the position of a double bond. 4-Androstenedione is naturally produced in the body by the glands and gonads. In addition to testosterone, it is also a precursor of estrone and estradiol

14.
11-Ketotestosterone
–
11-Ketotestosterone is an oxidized form of testosterone that contains a keto group at the C11 position. It is related to adrenosterone, a found in trace quantities in humans. In fish, 11-ketotestosterone functions as the endogenous androgenic sex hormone, in midshipman fish, 11-ketotestosterone is not present in females or Type II Males — Type II Males reach sexual maturation later, are less territorial, and have higher testosterone than Type I Males. In mammals, 11-ketotestosterone has similar potency to testosterone as an androgen and it is synthesized from 11β-hydroxyandrostenedione and, to a lesser extent, 11-ketoandrostenedione. 11-Ketoandrostenedione has notably been sold online as a prohormone, usually under the name 11-oxoandrostenedione

15.
Androstenediol
–
Δ5-Diol is a direct metabolite of the most abundant steroid produced by the human adrenal cortex, DHEA. It is less androgenic than the compound, Δ4-androstenediol, and has been found to stimulate the immune system. When administered to rats, Δ5-diol, in vivo, has approximately 1. 4% of the androgenicity of DHEA,0. 54% of the androgenicity of androstenedione, Δ5-Diol possesses potent estrogenic activity, similarly to DHEA and 3β-androstanediol. It has approximately 6% and 17% of the affinity of estradiol at the ERα and ERβ, the value of Δ5-diol as a radiation countermeasure is based mainly on its stimulation of production of white blood cells and platelets. The clinical trials with rhesus monkeys was successful, according to the Hollis-Eden report, only 12. 5% of the 40 Neumune-treated animals died versus 32. 5% in the placebo group. Hollis-Eden had applied for a contract from the U. S. Government under the BioShield Request for Proposals for radiation countermeasures, after being encouraged for 2.5 years that Neumune was in the competitive range, on March 9,2007, the RFP was canceled by HHS. According to HHS, the product was no longer in the competitive range, as a result, Hollis-Eden has now withdrawn from the radiation countermeasure field. 3α-Androstanediol 3β-Androstanediol Regenerative Medicine - Official Hollis-Eden Pharmaceuticals website New Scientist article on AED as an anti-radiation sickness drug

16.
Androstenedione
–
In turn, Δ4-dione is also a precursor of dihydrotestosterone, estrogens such as estradiol and estrone, and the neurosteroid 3α-androstanediol. Δ4-Dione is the precursor of the androgen and estrogen sex hormones. Δ4-Dione can be biosynthesized in one of two ways, the primary pathway involves conversion of 17α-hydroxypregnenolone to DHEA by way of 17, 20-lyase, with subsequent conversion of DHEA to Δ4-dione via the enzyme 3β-hydroxysteroid dehydrogenase. The secondary pathway involves conversion of 17α-hydroxyprogesterone, most often a precursor to cortisol, to directly by way of 17. Thus,17, 20-lyase is required for the synthesis of Δ4-dione, Δ4-Dione is produced in the adrenal glands and the gonads. The production of adrenal Δ4-dione is governed by adrenocorticotrophic hormone, whereas production of gonadal Δ4-dione is under control by the gonadotropins, in premenopausal women, the adrenal glands and ovaries each produce about half of the total Δ4-dione. After menopause, Δ4-dione production is about halved, due primarily to the reduction of the steroid secreted by the ovary, nevertheless, Δ4-dione is the principal steroid produced by the postmenopausal ovary. Some Δ4-dione is also secreted into the plasma, and may be converted in peripheral tissues to testosterone, Δ4-Dione is converted to either testosterone or estrogen. In males, conversion of Δ4-dione to testosterone requires the enzyme 17β-hydroxysteroid dehydrogenase, in females, Δ4-dione is released into the blood by theca cells. Conversion of Δ4-dione to estrogen requires the enzyme aromatase, Δ4-Dione is a substrate for estrogen production in granulosa cells which produce aromatase. Thus, theca cells and granulosa cells work together to form estrogens, levels are normally 30-200 ng/dL in females and 40-150 ng/dL in males. Androstanedione is a 5α-reduced metabolite of 4-androstenedione which serves as an intermediate in the biosynthesis of the androgen, Δ4-Dione has been found to possess estrogenic actions, similarly to other DHEA metabolites. However, in contrast to 5-androstenediol, its affinity for the receptors is very low. In juveniles aged 6-8 years old, there is a rise in androstenedione secretion along with DHEA called adrenarche and this rise in androstenedione and DHEA is hypothesized to play a crucial role for learning social, cultural and ecological skills, such as the development and understanding of sexual attraction. Δ4-Dione was manufactured as a supplement, often called andro for short. Sports Illustrated credits Patrick Arnold for introducing Δ4-dione to the North American market, Andro was legal and able to be purchased over the counter, and, as a consequence, it was in common use in Major League Baseball throughout the 1990s by record-breaking sluggers like Mark McGwire. The supplement is banned by the World Anti-Doping Agency, and from the Olympic Games, the International Olympic Committee in 1997 banned Δ4-dione and placed it under the category of androgenic-anabolic steroids. Δ4-Dione is banned by MLB, the NFL, USOC, NCA, barry R. McCaffrey, the director of the White Houses Office of National Drug Control Policy, attempted to determine whether Δ4-dione could be classified as an anabolic steroid in July 1999

17.
Boldenone
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Boldenone, also known as Δ1-testosterone, 1-dehydrotestosterone, or androsta-1, 4-dien-3-one-17β-ol, is a synthetic anabolic-androgenic steroid and the 1-dehydrogenated analogue of testosterone. Boldenone itself has never been marketed, as a drug, it is used as boldenone undecylenate. The activity of boldenone is mainly anabolic, with a low androgenic potency, boldenone will increase nitrogen retention, protein synthesis, increases appetite and stimulates the release of erythropoietin in the kidneys. Boldenone was synthesized in an attempt to create a long-acting injectable methandrostenolone, boldenone acts similar to methandrostenolone with fewer adverse androgenic effects. Although commonly compared to nandrolone, boldenone lacks progesterone receptor interaction, boldenone is among the substances banned by Major League Baseball, as well as most other major athletic organizations. Abraham Almonte was suspended for 80 games before the 2016 season after testing positive for boldenone, stephan Bonnar and Josh Barnett, mixed martial arts fighters from the UFC and PRIDE Fighting Championships, have also tested positive for the banned substance. After the World Extreme Cagefighting show on January 20,2006 Muay Thai turned MMA fighter Kit Cope also tested positive for boldenone, following the Strikeforce card on June 22,2007 former PRIDE and UFC fighter Phil Baroni tested positive for boldenone, as well as stanozolol. At a K-1 WGP event in Las Vegas on August 17,2007 two fighters, Rickard Nordstrand and Zabit Samedov, both tested positive for boldenone, alexandre Franca Nogueira tested positive for boldenone in July 2008. Antonio Silva tested positive for boldenone after his July 26,2008 fight against Justin Eilers in the EliteXC promotion, Silva was suspended by the California State Athletic Commission for a year and fined $2500. Justin Charles, a minor league baseball player with the Florida Marlins. Jon Conway and Jeff Parke of the New York Red Bulls both tested positive for the substance in 2008 and were suspended 10 games and fined 10% of their annual income and they are also the first to abuse MLS drug policy. Leading horse trainer Gai Waterhouse was fined $10,000 after being found guilty on May 15,2008 of presenting a horse to the races with a substance in its system. Her horse Perfectly Poised was found to have traces of the banned substance boldenone in its system after finishing second at Canterbury in April 2007, quinbolone, the 17-cyclopentenyl enol ether of boldenone

18.
Boldione
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Boldione, also known as androstadienedione or 1-dehydroandrostenedione, as well as 1, 4-androstadiene-3, 17-dione, is an important industrial precursor for various steroid hormones. In the United States the chemical is regulated as a Schedule III Controlled Substance, androstadienedione is an important industrial-scale precursor for a wide variety of steroid hormones within the estrane and androstane classifications. Androstadienedione is obtained in high yield from both plant and animal sterols by biotransformation, the chemical is a common byproduct derived from other processes. The product is produced in a single step via a simultaneous side-chain cleavage at the C17 position, in 2004 the United States Congress passed the Anabolic Steroid Control Act of 2005 which placed 36 steroids and over-the-counter prohormones into schedule III of the Controlled Substances Act. In this legislation boldenone was classified as a substance and boldione remained legal. In 2008, at the time of the proposal, these three substances were listed as ingredients in more than 58 dietary supplements which were available for purchase over the counter. Effective January 4,2010 these three chemicals, including boldione, were classified as Schedule III Controlled Substances and became illegal in the United States

19.
Clostebol
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Clostebol, also known as 4-chlorotestosterone, usually as the ester clostebol acetate, is a synthetic anabolic androgenic steroid. Clostebol is the 4-chloro derivative of the hormone testosterone. The chlorination prevents conversion to dihydrotestosterone while also rendering the chemical incapable of conversion to estrogen, clostebol is a weak AAS with potential use as a performance enhancing drug. It is currently banned by the World Anti-Doping Agency, oral Turinabol, combining the chemical structures of clostebol and dianabol, was widely used in the East German state-sponsored doping program. Clostebol acetate ointment has ophthalmological and dermatological use, a related anabolic steroid, methylclostebol, is a common additive in so-called dietary supplements, generally listed in the convoluted form 4-chloro-17α-methyl-androst-4-en-17β-ol-3-one. In 2016, urinalysis resulted in Therese Johaug testing positive for clostebol, in the US, clostebol is listed as a Schedule III substance

Graph that demonstrates the Michaelis–Menten kinetics model for the relationship between an enzyme and a substrate: one of the parameters studies in pharmacokinetics, where the substrate is a pharmaceutical drug.

Different forms of tablets, which will have different pharmacokinetic behaviours after their administration.

The time course of drug plasma concentrations over 96 hours following oral administrations every 24 hours. Note that the AUC in steady state equals AUC∞ after the first dose.